JP3257423B2 - Exhaust heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to purification of exhaust gas by raising the temperature of exhaust gas during a lean combustion operation of an in-cylinder injection type internal combustion engine in which fuel is injected directly into a combustion chamber, spark ignited and stratified combustion is performed. The present invention relates to an exhaust gas heating device that activates the device early.

[0002]

2. Related Art In recent years, in a spark ignition type internal combustion engine mounted on a vehicle, in order to reduce harmful exhaust gas components and improve fuel efficiency, fuel is directly supplied to a combustion chamber in place of a conventional intake pipe injection type. Various direct injection gasoline engines have been proposed. In an in-cylinder injection type gasoline engine, for example, by injecting fuel from a fuel injection valve into a cavity (recess) provided at the top of the piston, an air-fuel ratio near the stoichiometric air-fuel ratio is mixed around the ignition plug at the time of ignition. I'm generating the energy. This makes it possible to ignite even with a lean air-fuel ratio as a whole, thereby reducing CO and HC emissions and greatly improving fuel efficiency during idling operation and low load driving.

In such a gasoline engine,
The compression stroke injection mode and the intake stroke injection mode are switched according to the operating state of the engine, that is, the engine load. By switching the control mode in this manner, during low load operation, the compression stroke injection mode is set to inject fuel mainly during the compression stroke, and to locally mix the fuel near the stoichiometric air-fuel ratio around the ignition plug or in the cavity. Thus, good stratified combustion can be performed even with a lean air-fuel ratio as a whole (this control mode is also referred to as a compression lean mode).

[0004] On the other hand, during a medium to high load operation, the intake stroke injection mode is set to inject fuel mainly during the intake stroke.
An air-fuel mixture having a uniform air-fuel ratio is formed in the combustion chamber, and a large amount of fuel is burned to secure an output required during acceleration or high-speed running, similarly to an intake pipe injection type gasoline engine. When a cold start of such an in-cylinder injection type internal combustion engine or during a low-load operation in an environment where the outside air temperature is low, an exhaust gas purification device (also simply referred to as a catalyst) disposed in an exhaust passage is easily activated after startup. The catalyst that has not been activated or has been activated is likely to be deactivated due to, for example, the above-described compression lean mode operation (the amount of intake air is larger than the fuel injection amount, and the exhaust temperature may be lowered due to lean combustion). There is a problem. In order to cope with such a problem, various methods for raising the exhaust gas temperature to activate the catalyst early have been proposed.

For example, Japanese Patent Application Laid-Open No. Hei 8-100638 proposes a method of reliably reburning fuel additionally injected during an expansion stroke in a cylinder without an additional device (such as a spark plug). In this proposal, in addition to the normal fuel injection (combustion injection for the main combustion), additional fuel is injected during the early to middle stages of the expansion stroke, and the additional fuel is ignited by the flame propagation of the main combustion. , It is intended to raise the exhaust gas temperature. According to this method, the exhaust gas temperature can be made higher than usual without restarting the ignition plug at the time of reburning, and the catalyst can be activated early.

[0006]

However, in the above-mentioned proposed method, the injection timing of the additional fuel during the expansion stroke can be reliably ignited by the propagation of the flame of the main combustion in order to surely recombust the fuel in the cylinder. It must be set at a time from the beginning to the middle of the expansion stroke (the crank angle is described as 10 ° ATDC to 80 ° ATDC in the above-mentioned Japanese Patent Application Laid-Open No. Hei 8-100638). If the additional fuel is injected at an early stage of such an expansion stroke, a part of the heat energy generated by the reburning of the additional fuel is taken away by the expansion work, and the original purpose of raising the exhaust gas temperature is improved. Will not be implemented. In such a case, additional fuel is increased in order to obtain a sufficient exhaust gas temperature increase rate, which leads to an increase in extra fuel, which is not preferable.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust gas heating apparatus capable of efficiently and surely heating exhaust gas while minimizing fuel consumption. It is in.

[0008]

In order to achieve the above object, the invention according to claim 1 is provided with a fuel injection valve for directly injecting fuel into a combustion chamber, and injecting fuel from the fuel injection valve at least during a compression stroke. In an exhaust gas heating device for a direct injection internal combustion engine that performs stratified combustion by spark ignition, an amount of fuel that locally generates an over-rich mixture around a spark plug during engine operation that requires exhaust gas heating. Fuel injection control means for controlling the fuel injection valve so as to inject the fuel in the compression stroke, and when the fuel injection valve is controlled by the fuel injection control means, the fuel is injected and spark ignited in the compression stroke. The fuel is overwhelmed around the spark plug.
And an engine control means for controlling engine control parameters so that the incomplete combustion in the first state is caused and mixed with excess oxygen in the cylinder in accordance with the in-cylinder flow and burn.

As described above, when stratified combustion is established in a state where the air-fuel ratio around the ignition plug is locally over-rich by the fuel injection control means, when ignition is performed near the compression top dead center of the piston, The fuel does not completely burn around the spark plug due to the local shortage of air, and the engine control means controls the engine control parameters.
Part of the incomplete combustion occurs due to the over-rich state , and incomplete combustion products such as HC and CO are generated. Thereafter, when the piston starts to descend in the expansion stroke, these incompletely combusted substances diffuse to the surroundings in the combustion chamber. At this time, the incompletely combusted material has an activation energy of such a degree that it exists in the high temperature atmosphere after combustion and can be burned.
O in air present in the combustion chamber away from the spark plug
₂ Reacts favorably with (oxygen) and reburns. However, since this reburning is slow, the exhaust gas temperature is suitably raised without being used for expansion work, and therefore the catalyst is quickly heated and activated early.

This is similar to the secondary air system (a system in which air is supplied from an air pump to an exhaust passage and the temperature of the exhaust gas is raised) (at an ambient temperature of about 450 ° C. and under the presence of HC and CO). When air is supplied, it reburns and the exhaust gas temperature rises). However, in the case of the present invention, unlike the secondary air system, an additional device such as an air pump is not particularly required, which does not lead to an increase in cost.

Further , in the invention according to claim 2, the engine
Control means for controlling the fuel injection by the fuel injection control means;
When the valve is being controlled, the
The fuel injection timing as an engine control parameter
Fuel in compression stroke during engine operation when temperature is not required
It is characterized in that it is delayed from the injection timing. this
As described above, the fuel injection during the compression stroke is performed by the engine control means.
The timing is delayed and the ignition plug is controlled by the fuel injection control means.
With the air-fuel ratio around the engine locally overrich
When stratified combustion is established, a point near the compression top dead center of the piston
When a fire is implemented, local air shortage and fuel
Plug due to insufficient atomization time due to delay in fuel injection timing
Around, fuel combustion becomes more imperfect, HC, CO, etc.
A lot of incomplete combustion products are generated. After that, the expansion stroke
When the piston begins to descend, incomplete combustion occurs as described above.
The object will reburn, and the exhaust temperature will rise appropriately
The catalyst is quickly heated and activated early. According to a third aspect of the present invention, in the second aspect, the engine control means determines that the fuel injection timing is required to increase the exhaust gas temperature.
Than the fuel injection timing of the compression stroke during engine operation
When it is delayed, it is characterized in that the <br/> ignition timing of the engine control parameter, to delay than the ignition timing at the time exhaust gas Atsushi Nobori is required Tei no engine operation.
As a result, the combustion becomes slow and the fuel injection timing is delayed.
In addition, it is possible to more effectively raise the exhaust gas temperature. Further, in the invention according to claim 4, the fuel injection control means includes a fuel injection control unit.
The section between the initial intake stroke to the initial of the compression stroke, locally the over-rich mixture of the compression stroke
The fuel injection valve is controlled to inject prior to the fuel injection for generation .

As described above, when a part of the fuel is previously supplied into the combustion chamber at a stage before the fuel is injected during the compression stroke,
Since the air-fuel mixture formed by the fuel supplied in advance is lean, the flame of the main combustion cannot propagate and remains in an unburned state. However, the lean mixture receives heat of compression and main combustion, and causes a so-called preflame reaction to change into an active chemical reaction species. Accordingly, active chemical reactive species in the combustion state immediately before with O ₂ or the like in the combustion chamber (e.g., CHO, H
₂ O ₂ , OH, etc.), that is, a large amount of preflame reaction products. Then, when the incompletely combusted material diffuses around in the combustion chamber during the expansion stroke, the incompletely combusted material reacts with O ₂ present apart from the spark plug and recombustion proceeds. The flame reaction product plays the role of an ignition inducer, and the reburning proceeds better. As a result, the exhaust gas temperature is further increased, and thus the catalyst is activated earlier.

[0013] In the invention of claim 5, the amount of <br/> injection should do fuel to the preceding, 10% of the total amount of injection should do fuel to gulp cylinder per cycle of the internal combustion engine 40 %. Therefore, prior to injection
Should do fuel quantity is in the range 10% to 40% of fuel total quantity to be injected in one stroke cylinder per cycle of the internal combustion engine, the combustion chamber, and suitably ignited a level that does not contribute to the expansion work It is possible to have a proper amount of a preflame reaction product that can serve as an inducer and raise the temperature of the exhaust gas.

Further, in the invention of claim 6 , further comprising an air amount adjusting means for adjusting the amount of air introduced into the combustion chamber, wherein the air amount adjusting means operates at least in an engine operation which requires an exhaust temperature rise. Occasionally , the air amount is increased, and the fuel injection control means is provided to the air amount adjustment means.
The amount of fuel injection is increased size depending on the introduction amount of air increased size due
It is characterized by controlling the urchin the fuel injection valve.
Therefore, when the exhaust gas temperature rises, the fuel injection amount in the compression stroke is increased in accordance with the increase in the air amount, and the fuel injection control is performed.
The exhaust gas heating effect is further improved. The invention of claim 7
Then, in claim 1, the engine control means is
The fuel injection valve is controlled by the fuel injection control means.
Ignition, as an engine control parameter
Period during engine operation when exhaust temperature rise is not required.
It is characterized by delaying from the fire time. to this
The combustion becomes slower, and more effective exhaust gas heating is possible.
It is said.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG.
FIG. 1 is a schematic configuration diagram illustrating a control device of a direct injection gasoline engine mounted on a vehicle, and is a diagram illustrating an exhaust gas heating device according to the present invention. In FIG. 1, reference numeral 1 denotes an in-cylinder in-cylinder in-line four-cylinder gasoline engine (hereinafter simply referred to as an engine) of a spark ignition type and directly injects fuel into a combustion chamber. Each step of 1
An internal combustion engine provided during the cycle, that is, a four-cycle engine. In the engine 1, an intake device, an EGR device 10, etc., including the combustion chamber 1a, are designed exclusively for in-cylinder injection.

The cylinder head of the engine 1 is also provided with an electromagnetic fuel injection valve 8 together with an ignition plug 35 for each cylinder, so that fuel is directly injected into the combustion chamber 1a. On the top surface of the piston 1b which reciprocates by sliding in the cylinder, a hemispherical depression, that is, a cavity 1c, is located near the top dead center (TDC) where fuel spray from the fuel injection valve 8 reaches. Are formed. Also,
The theoretical compression ratio of the engine 1 is set higher (about 12 in this embodiment) than that of the intake pipe injection type. A DOHC 4-valve valve mechanism is employed as a valve operating mechanism. An intake-side camshaft and an exhaust-side camshaft are rotatably held above the cylinder head to drive the intake and exhaust valves 4 and 5, respectively. I have.

An intake port 2a is formed in the cylinder head in a substantially upright direction so as to pass through between the two camshafts. An intake flow passing through the intake port 2a causes a so-called reverse tumble flow in the combustion chamber 1a. A flow can be generated. On the other hand, the exhaust port 3a is formed in a substantially horizontal direction similarly to a normal engine, but has a large-diameter EGR port (not shown) branched diagonally.

In the figure, reference numeral 19 denotes a water temperature sensor for detecting a cooling water temperature Tw, and reference numeral 21 denotes a crank angle signal SGT at a predetermined crank position (5 ° BTDC and 75 ° BTDC in this embodiment) of each cylinder. Reference numeral 34 denotes an ignition coil for outputting a high voltage to the ignition plug 35. Note that a camshaft that rotates at half the number of revolutions of the crankshaft is provided with a cylinder discrimination sensor (not shown) that outputs a cylinder discrimination signal SGC.
Based on the signal from this sensor, it is determined which cylinder the crank angle signal SGT belongs to.

As shown in FIG. 1, an air cleaner 6a, a throttle body 6b, a stepper motor type idle speed control valve (idle adjustment valve) 16 is provided to the intake port 2a via an intake manifold 2 having a surge tank 2b. Is connected. Further, the intake pipe 6 is provided with a large-diameter air bypass pipe 50a for introducing intake air to the intake manifold 2 bypassing the throttle body 6b, and a linear solenoid type large air bypass pipe is provided in the pipeline. A valve (ABV, that is, air amount adjusting means) 50 is provided. The air bypass pipe 50a has a flow passage area similar to that of the intake pipe 6, and when the ABV 50 is fully opened, the required amount of intake air in the low to medium speed range of the engine 1 can flow. On the other hand, the idle adjustment valve 16
It has a flow passage area smaller than 0 and uses the idle adjustment valve 16 when adjusting the intake air amount with high accuracy.

The throttle body 6b includes a butterfly type throttle valve 7 for opening and closing a flow path, a throttle sensor 14 for detecting accelerator opening information by detecting a throttle opening θth, and an idle sensor for detecting a fully closed state. A switch 15 is provided. Air cleaner 6
a, an intake air temperature sensor 1 for obtaining an intake air density.
2. An atmospheric pressure sensor 13 is provided, and the atmospheric pressure Pa,
A signal corresponding to the intake air temperature Ta is output. Further, a Karman vortex airflow sensor 11 is disposed near the inlet of the intake pipe 6, and outputs a vortex generation signal proportional to the volume air flow rate Qa per intake stroke.

The above-mentioned EGR port has a large-diameter EGR port.
It is connected downstream of the throttle valve 7 and upstream of the intake manifold 2 via a GR pipe 10b, and a stepper motor type EGR valve 10a is disposed in the pipeline. On the other hand, the exhaust port 3a is connected to an exhaust manifold 3 to which an O ₂ sensor 17 is attached, and further connected to a catalytic converter 9 as an exhaust purification catalyst and an exhaust pipe 3b having a muffler (not shown). ing. The O ₂ sensor 17 detects the oxygen concentration in the exhaust gas and outputs a detection signal. Further, a catalyst temperature sensor 26 for detecting the temperature of the catalyst or the vicinity thereof, that is, the catalyst temperature Tcc is attached to the downstream side of the catalytic converter 9.

That is, from the combustion chamber 1a to the exhaust manifold 3
After the three harmful components of CO, HC and NOx in the exhaust gas are purified by the catalytic converter 9,
The sound is muted by the muffler and released to the atmosphere. In particular, the present engine 1 is an engine that can perform the economizing operation while keeping the air-fuel ratio on the lean side (lean side).
At the time of this lean combustion operation, NOx in exhaust gas cannot be sufficiently purified only by a normal three-way catalyst. Therefore, the catalytic converter 9 is a combination of a lean NOx catalyst 9a and a three-way catalyst 9b. See Lean NOx
Downstream of the catalyst 9a, CO,
A three-way catalyst 9b having a three-way function capable of purifying HC and NOx is provided. That is, while the three-way catalyst 9b is arranged upstream of the lean NOx catalyst 9a so as not to hinder the NOx purification by the lean NOx catalyst 9a, the CO that cannot be sufficiently purified by the lean NOx catalyst can be obtained.
And HC are surely purified. When the lean NOx catalyst also has a three-way function, only one lean NOx catalyst may be provided.

A fuel tank (not shown) is provided at the rear of the vehicle body. Then, the fuel stored in the fuel tank is sucked up by an electric low-pressure fuel pump and sent to the engine 1 side through a low-pressure feed pipe. The fuel supplied to the engine 1 is supplied to a high-pressure fuel pump (not shown) attached to a cylinder head via a high-pressure feed pipe and a delivery pipe.
The fuel is supplied to each fuel injection valve 8.

An electronic control unit (ECU) is provided in the vehicle interior.
The ECU 23 is provided with an input / output device (not shown) and a storage device (ROM, RAM, nonvolatile RAM) for storing control programs, control maps, and the like.
Etc.), a central processing unit (CPU), a timer counter, and the like, and perform overall control of the engine 1. ECU2
The input side of 3 is connected to switches and the like for detecting the operating status of an air conditioner, a power steering device, an automatic transmission, etc., which are loads on the engine 1 when activated,
Each detection signal is supplied. In addition, on the input side of the ECU 23, in addition to the various sensors and switches described above, many switches and sensors (not shown) are connected to the input side, and various warning lights and many devices are also provided on the output side. Are connected.

The ECU 23 determines the fuel injection mode, the fuel injection amount, the fuel injection end timing, the ignition timing, the amount of EGR gas introduced, etc., based on the input signals from the various sensors and switches described above. The drive control of the fuel injection valve 8, the ignition coil 34, the EGR valve 10a and the like is performed. Less than,
The normal control of the engine 1 in the control device for a direct injection gasoline engine configured as described above, that is, the temperature rise of the exhaust gas
Is not required, and the control when the exhaust gas temperature raising control described later is not performed will be briefly described.

When starting the engine in a cold state, the ECU
23 selects an intake stroke injection mode and injects fuel so as to have a relatively rich air-fuel ratio. At this time, the ECU
At 23, the ABV 50 is closed at the time of startup, so that the intake air to the combustion chamber 1a is supplied from the gap of the throttle valve 7 and the idle adjustment valve 16. And, after starting, the cooling water temperature TW
Until the pressure rises to a predetermined value, the ECU 23 selects the intake stroke injection mode to inject fuel in the same manner as at the time of starting, and also continuously closes the ABV 50. In addition, the control of the idle speed according to the increase or decrease of the load of the auxiliary equipment such as the air conditioner is performed by the idle adjusting valve 16 (the ABV 50 is also opened as necessary) as in the intake pipe injection type. Furthermore, when the predetermined temperature elapses and the O ₂ sensor 17 reaches the activation temperature, the ECU 23 starts the air-fuel ratio feedback control according to the output voltage of the O ₂ sensor 17, and purifies the harmful exhaust gas component by the catalytic converter 9. Let it. As described above, when the engine is cold, substantially the same fuel injection control as that of the intake pipe injection type is performed.

When the warm-up of the engine 1 is completed, the ECU 2
3 is based on the target average effective pressure (target load) Pe obtained from the throttle opening θth and the like and the engine rotation speed Ne.
The current fuel injection control area of the engine 1 is searched from the fuel injection control map of FIG. 2, the fuel injection mode and the fuel injection amount are determined, the fuel injection valve 8 is driven, and the ABV 50
Also, valve opening control of the EGR valve 45 is performed.

For example, during low-load / low-speed operation such as idling operation, the operation region becomes a compression stroke injection lean region indicated by oblique lines in FIG. 2, and the ECU 23 selects the compression stroke injection mode, and sets the ABV 50 and the EGR valve 10a. Is opened according to the operating state, and a lean air-fuel ratio (here, 2
(About 0 to 40). In this case, since the intake air flowing from the intake port 2a forms a reverse tumble flow in the combustion chamber 1a, the injected fuel spray is substantially stored in the cavity 1c of the piston 1b without being diffused. As a result, the ignition plug 3
A mixture around the stoichiometric air-fuel ratio is formed around 5, and ignition is possible even with an extremely lean air-fuel ratio as a whole (for example, about 50 in overall air-fuel ratio). As a result, the emission of CO and HC becomes extremely small, and the emission of NOx is also reduced by the recirculation of exhaust gas. Further, the fuel consumption is greatly improved due to the reduction of the pumping loss caused by opening the ABV 50 and the EGR valve 10a. Also, here, since the control of the idle speed according to the increase or decrease of the load is performed by increasing or decreasing the fuel injection amount,
Control response is also very high.

When the vehicle is running at low to medium speeds, the operating range is the intake stroke lean region or the stoichiometric feedback region (the stoichiometric air-fuel ratio feedback control region, hereinafter referred to as S-line) in accordance with the load condition and the engine speed Ne. Therefore, the ECU 23 selects the intake stroke injection mode and injects fuel so as to have a predetermined air-fuel ratio.

That is, in the intake stroke lean region, A is set so that the air-fuel ratio becomes relatively lean (for example, about 20 to 23).
By controlling the valve opening amount and the fuel injection amount of the BV50, the SF / B
In the range, the ABV 50 and the EGR valve 10a are controlled to open and close (however, the opening and closing control of the EGR valve 10a is controlled by S / F /
The air-fuel ratio feedback control is performed in accordance with the output voltage of the O ₂ sensor 17.

At the time of rapid acceleration or high-speed running, the operation area is an open loop area in FIG.
The intake stroke injection mode is selected, the ABV 50 is closed, and fuel is injected so as to have a relatively rich air-fuel ratio in accordance with the throttle opening θth, the engine speed Ne, and the like. Further, when the vehicle is coasting during middle-to-high speed traveling, the operation region is the fuel cut region in FIG.
Stops the fuel injection completely. The fuel cut is
If the engine rotation speed Ne falls below the return rotation speed or if the driver depresses the accelerator pedal, the operation is immediately stopped.

Next, a control procedure of the exhaust gas heating apparatus according to the present invention will be described. Here, Example 1 and Example 2
Will be described. Note that this exhaust gas temperature raising control is appropriately performed in response to a request for exhaust gas temperature raising regardless of the execution of the normal control described above. First, a first embodiment will be described. Referring to FIG. 3, there is shown a flowchart of a main routine of the exhaust gas temperature raising control executed by the ECU 23, which will be described below with reference to FIG. Note that this routine is repeatedly executed each time the crank angle sensor 21 outputs the crank angle signal SGT while the above-described normal control is being executed.

First, at step S10, the catalyst temperature Tc
c, cooling water temperature Tw, intake air flow rate Qa, throttle opening θ
Th, various engine operation state quantities such as the engine speed Ne, the atmospheric pressure Pa, and the intake air temperature Ta are read. Next step S
Step 12 and steps S18 to S22 are steps for determining whether or not to perform the exhaust gas temperature raising control. When all the conditions of each of these steps are satisfied, the exhaust gas temperature raising control is started.

In step S12, the operation region is in a lean combustion operation region such as a compression stroke injection lean region or an intake stroke lean region, and the change in the throttle opening θth is small, the vehicle is in a steady running state, and stratified combustion or It is determined whether or not the premixed lean combustion is being performed. That is, it is determined whether or not the operation state is the lean combustion operation state.
When the determination result is false (No), it is determined that the operation region is not the lean combustion operation region, and that the change in the throttle opening θth is large and that the stratified combustion or the premixed lean combustion is not performed, that is, the premixed combustion is performed. (Operation near the stoichiometric air-fuel ratio)
If, the routine proceeds to step S14, where the normal control described above, that is, the normal fuel injection control and the normal ignition timing control in each operation region are performed.

In step S16, a timer TM described later is reset to a value of zero. If the result of the determination in step S12 is true (Yes), the operation region is in a lean combustion operation region such as a compression stroke injection lean region or an intake stroke lean region, and the change in throttle opening θth is small and the vehicle is in a steady running state. If it is determined that stratified combustion or premixed lean combustion is being performed in this case, it is determined that exhaust gas temperature raising control is necessary, and the process proceeds to step S18.

That is, when the air-fuel ratio is a lean air-fuel ratio (for example, 2
(Approximately 0 to 40), the generation of heat due to combustion is originally small as described above. Therefore, in such a lean combustion operation state, especially in a stratified combustion state, the exhaust gas temperature Tex remains low. Will be held in
Therefore, in such a case, the catalytic converter 9
Is lower than the catalyst lower limit temperature T1 at which the catalyst function is maintained.
It is determined that there is a possibility that the temperature will be lower than (e.g., 400 [deg.] C.), and the process proceeds to step S18 to perform the exhaust gas temperature increase control.

In step S18, the throttle opening θth
Is constant and a predetermined time has elapsed. That is, here, the engine is in the lean combustion operation state and the throttle opening degree θ
It is determined whether or not th is constant without change and the catalyst temperature Tcc of the catalytic converter 9 is more likely to decrease.
If the determination result is false, the process proceeds to step S14 to perform the above-described normal control.

On the other hand, if the decision result in the step S18 is true,
When it is determined that the predetermined time has elapsed while the throttle opening θth is kept constant, for example, when the operation region is in the compression stroke injection lean region and the idle operation is continued for the predetermined time, the exhaust gas temperature is raised. It is considered that control is necessary, and the process proceeds to step S20. In step S20, a timer TM, which will be described later, starts aging at the same time as the start of the exhaust gas temperature raising control.
It is determined whether or not the counted time is less than the predetermined time TM1. Once the exhaust gas temperature rise control is performed, the process proceeds to step S20.
Is false and the time measured by the timer TM is the predetermined time TM
If it is determined that the number has reached 1, the above step S
Proceeding to 14, the above-described normal control is also performed.

On the other hand, if the decision result in the step S20 is true,
When the time has not passed so long after the exhaust gas temperature raising control has been performed, and the time counted by the timer TM is less than the predetermined time TM1, or when the timer TM has been reset to the value 0 by executing the step S16. Then, the process proceeds to step S22. In step S22, it is determined whether the catalytic converter 9 is in an active state. That is, it is determined whether or not the catalyst temperature Tcc of the catalytic converter 9 is equal to or higher than the activation lower limit temperature T1 (for example, 400 ° C.). If the determination result is true and the catalyst temperature Tcc is lower than the activation lower limit temperature T1 (for example, 4
If the temperature is equal to or higher than (00 ° C.), it is not necessary to perform the exhaust gas temperature raising control. In this case, the process proceeds to step S14 to perform the normal control described above.

On the other hand, if the result of the determination in step S22 is false, the condition that requires the exhaust gas temperature rise control is satisfied, so the routine proceeds to step S24, where the exhaust gas temperature rise control is performed. At this time, if the operation state before the exhaust temperature raising control is performed is the compression stroke injection mode (stratified combustion), the fuel injection amount, the fuel injection timing, the ignition timing, and the like are increased while the torque step is not generated. In the case of the intake stroke injection mode (premixed lean combustion), the fuel injection amount, the fuel injection timing, the ignition timing, and the like are switched to the compression stroke injection mode while the torque step is not generated. Normally, the opening of the ABV 50 or the like is substantially constant between the normal control before the exhaust gas temperature raising control and the exhaust gas temperature raising control, and the opening / closing control is not particularly performed.

In the exhaust gas temperature raising control in step S24, FIG.
The exhaust gas temperature raising control routine is executed. Hereinafter, the exhaust gas temperature raising control will be described with reference to FIG. In the exhaust gas temperature raising control, the fuel injection is performed in the compression stroke as in the compression stroke injection mode of the normal control. In step S30, the fuel injection timing (engine control parameter)
Is set for the normal control (engine control means). That is, here, in the compression stroke injection mode at the time of the normal control, for example, the fuel injection timing set to 57 ° BTDC is greatly retarded to 20 ° BTDC to TDC. Here, the fuel injection timing is desirably 15 ° BTDC
It is better to be ~ 5 ° BTDC.

In step S32, the fuel injection amount is set so as to be locally rich in the cavity 1c of the piston 1b (fuel injection control means).
That is, in the case of the compression stroke injection mode, the air-fuel ratio in the cavity 1c is locally made to be close to the stoichiometric air-fuel ratio. Here, the air-fuel ratio in the cavity 1c is rich (for example, rich). , About 8 to 10). At this time, the overall air-fuel ratio is the stoichiometric air-fuel ratio or slightly lean (for example, about 14 to 18).
It is said.

Further, in the next step S34, the ignition timing (engine control parameter) is set to a retard (delay) with respect to the case of the normal control similarly to the fuel injection timing (engine control means). That is, here, for example, in the compression stroke injection mode during normal control, for example, 20 ° BTDC to 2 °
The ignition timing of 5 ° BTDC is greatly retarded from 15 ° BTDC to 5 ° ATDC in accordance with the fuel injection timing. here,
The ignition timing is preferably 10 ° BT according to the fuel injection timing.
It is preferable to set DC to TDC.

In the next step S36, fuel injection is performed based on the set fuel injection timing and fuel injection amount, and in step S38, ignition is performed based on the set ignition timing set. Here, referring to FIG. 5, the combustion chamber 1 when the exhaust gas temperature raising control is performed is described.
(a) to (d) show the state in a in chronological order, and the operation of the exhaust gas temperature raising control will be described below with reference to FIG.

First, as shown in FIG. 5A, in the compression stroke, fuel is more than usual by the fuel injection valve 8, that is, the local air-fuel ratio is rich (for example, about 8 to 10).
It is injected so that it becomes. At this time, since the fuel injection timing is retarded from 20 ° BTDC to TDC as described above,
The piston 1b is located at a position higher than a normal piston position (broken line).

Then, as shown in FIG.
Ignition is performed between ° BTDC and 5 ° ATDC. By the way, normally, the crank angle difference between the fuel injection timing (57 ° BTDC) and the ignition timing (20 ° BTDC to 25 ° BTDC) is 3
When the ignition is performed, the fuel spray reaches the ignition plug 35. However, when the exhaust gas temperature rise control is performed, the fuel injection timing (20 ° BTDC
~ TDC) and ignition timing (15 ° BT
The difference in crank angle from DC to 5 ° ATDC) is set to 5 °, as shown in the figure, such that the tip of the fuel spray finally reaches the spark plug 35 at the time of ignition.
That is, even if ignition is performed when the air-fuel ratio around the ignition plug 35 is completely rich, the fuel does not satisfactorily ignite due to the small amount of air, while the fuel This is because, if the ignition is performed at the time when the fuel reaches the ignition plug 35, there is sufficient air around the ignition plug 35, so that the ignition is performed well and the combustion is started.

When the combustion is started in this way, the combustion flame at the tip of the fuel spray propagates as shown in FIG. 3C by a hot flame reaction between the fuel spray in the cavity 1c and O ₂ , The combustion gases begin to expand. However, at this time, since the air-fuel ratio in the cavity 1c is locally rich (for example, about 8 to 10), there is not enough O ₂ for combustion, and therefore, part of the fuel spray is It becomes over-rich and incompletely burns, resulting in incompletely combusted substances such as HC and CO.

The piston 1 is moved by the expansion of the combustion gas.
b is pushed down, but at this time,
Incomplete combustion products such as HC and CO generated by total combustion
As shown in FIG. 4D, the cavity 1c is formed in the combustion chamber 1a.
It will diffuse from inside to surroundings. By the way, at this point
Then, in the combustion chamber 1a other than the cavity 1c,
There is air taken in during the stroke, and
The burnt matter is O2 in this air. _TwoReacts well with
Will be implemented. This recombustion of incompletely combusted materials causes
Since the pressure in the combustion chamber 1a decreases more rapidly,
It is relatively slow without progress, and almost no expansion work
No contribution. However, on the one hand its combustion
Will continue gently until the transition to the exhaust stroke.
You.

Referring now to FIG. 6, there is shown in a graph the relationship between the change in the crank angle from the vicinity of TDC and the heat release rate in the expansion stroke, and the solid line in FIG. The dashed line indicates the heat generation rate when the normal control is performed in the compression stroke injection mode. As is clear from the figure, when the exhaust gas temperature rise control is performed (solid line), the combustion at the time of ignition is slower than when the normal control is performed (dashed line), but during the expansion stroke, the heat is increased. The incidence is kept high.

Therefore, the exhaust gas temperature Tex can be satisfactorily raised to the temperature T2 (for example, about 800 ° C.).
The catalytic converter 9 can be quickly heated and activated early. When the exhaust gas temperature raising control is started in this way, the timer TM is set in step S26 in FIG. 3, and the time elapsed since the execution of the exhaust gas temperature raising control is measured.

Then, the result of the determination in step S20 is false, that is, it is determined that the time measured by the timer TM has reached the predetermined time TM1, or the result of determination in step S22 is true, and the catalytic converter 9 is activated. If it is determined that the exhaust gas temperature rise control has been completed, the exhaust gas temperature raising control ends, and the timer TM is reset to the value 0 in step S16. Next, a second embodiment will be described.

Since the second embodiment differs from the first embodiment only in the exhaust gas temperature control, only the exhaust gas temperature control will be described here. In the second embodiment, at the time of exhaust gas temperature rise control, a part of fuel is injected in advance in the intake stroke in addition to fuel injection in the compression stroke (hereinafter referred to as main injection) (hereinafter referred to as intake stroke preceding injection). That is, here, two-stage injection of the intake stroke preceding injection and main injection is performed for the single-stage injection of the first embodiment (fuel injection control means).

Referring to FIG. 7, there is shown an exhaust gas temperature raising control routine according to the second embodiment, which will be described below with reference to FIG. In steps S40 and S42, the fuel injection timing of the main injection is set to a retard with respect to the case of the normal control, and the fuel injection amount of the main injection is also set to the cavity of the piston 1b. 1
Locally rich in c (for example, about 8 to 10)
Is set to be

In the next step S44, the fuel injection timing and fuel injection amount for the intake stroke advance injection are set. The fuel injection timing of the intake stroke preceding injection may be at the beginning of the compression stroke because the fuel injection amount is small and the fuel is atomized in a short time. Desirably, the fuel injection timing is set at the beginning of the intake stroke, and here, for example, 320 ° BTDC
It is said.

The fuel injection quantity of the intake stroke preceding injection is:
The total fuel injection amount during one cycle (the amount of fuel to be injected)
(Total amount) is set to 10% to 40%. Here, FIG. 8 is a graph showing the relationship between the fuel ratio and the exhaust temperature Tex with respect to the total fuel injection amount during the intake stroke advance injection, and FIG. 9 is a graph showing the intake stroke advance injection. Fuel ratio and unburned hydrocarbon TH from the exhaust port 3a
The relationship with the amount of C (Total Hydrocarbon) emission is shown in a graph. According to these graphs, when the fuel injection amount of the intake stroke preceding injection is set in the range of 10% to 40%, the exhaust gas temperature Tex is reduced to the temperature T2 (for example, about 800 ° C.) achieved in the first embodiment. It can be seen that the emission of unburned hydrocarbon THC, which is a harmful substance, into the atmosphere can be suppressed to a relatively small value while the value is larger than that in the case of (1). Therefore, here, the fuel injection amount of the intake stroke preceding injection is set to 10% to 40% of the total fuel injection amount.

Further, referring to FIG.
%, The exhaust temperature Tex is maximized, and the emission of unburned hydrocarbon THC is minimized. Therefore, the fuel ratio of the intake stroke preceding injection is desirably about 20% of the total fuel injection amount. In the next step S46, as in the case of the first embodiment, the ignition timing is retarded with respect to the case of the normal control.

Then, in step S48, first, the intake stroke preceding injection is performed. Here, referring to FIG. 10, the state in the combustion chamber 1a from the intake stroke to the early stage of the compression stroke when the intake stroke preceding injection is performed in the intake stroke is shown in time series (e) to (g). The operation of the intake stroke preceding injection will be described below with reference to FIG.

First, as shown in FIG. 5E, at 320 ° BTDC in the intake stroke, 10% to 40% of the fuel is injected as described above. Then, the fuel that has been pre-injected in the intake stroke as described above is diffused in the combustion chamber 1a together with the inertial airflow (tumble flow) due to the intake according to the lowering of the piston 1b, as shown in FIG.
At this time, the fuel injected in advance in the intake stroke receives heat from compression and main combustion due to the rise of the piston 1b, and is an active chemical reaction species (for example, CHO, CHO, etc.) effective to promote a chain reaction immediately before combustion. H ₂ O ₂ , OH, etc.), ie, a preflame reaction product.

Then, the pre-flame reaction product is supplied to the combustion chamber 1a.
In the state where the inside is filled, as shown in FIG. 9 (g), the process shifts to the compression stroke, and the piston 1b rises. When the piston 1b rises in this way, step S50 in FIG.
In step S52, the main fuel is injected, and ignition is performed. The state of the combustion chamber 1a at this time is as described in the first embodiment with reference to FIG. Then, as shown in FIG. 5D, the incompletely combusted material diffuses from the cavity 1c to the surroundings in the combustion chamber 1a as the piston 1b descends. At this time, since the pre-flame reaction product floats in the combustion chamber 1a as described above, the pre-flame reaction product plays a role of an ignition inducing agent. Also, the combustion of the incompletely burned material is assisted and the reburning continues.

As described above, in the second embodiment, the two-stage injection of the intake stroke advance injection and the main injection is performed in the intake stroke and the compression stroke, respectively. The effect of this will be described in more detail. Referring to FIG. 11, a graph similar to that of FIG. 6 is shown. In FIG. 11, a heat generation rate when the exhaust gas temperature rise control is performed in the two-stage injection of the second embodiment is indicated by a dotted line. It is shown. Further, in the same drawing, the heat generation rate when the exhaust gas temperature raising control of the first embodiment is performed is indicated by a solid line, and the heat generation rate when the normal control is performed in the compression stroke injection mode is indicated by a dashed line. ing.

As is clear from the figure, in the case of the second embodiment (dotted line) in which the exhaust gas temperature rise control by the two-stage injection is performed, the heat release rate has a larger expansion stroke than in the case of the first embodiment (solid line). Is higher overall. This means that incompletely combusted substances such as HC and CO generated by incomplete combustion are generated in the combustion chamber 1a.
In this case, the gas diffuses from the cavity 1c to the surroundings, reacts with O _2, and is reburned (see FIG. 5D). In the case of the second embodiment, however, the combustion chamber 1a there exists a pre-flame reaction product by the intake stroke prior injection, and thus would play a role in ignition induction agent so that the pre-flame reaction product described above, the incomplete combustion product reburning is O ₂ This is because it is promoted better than in the case of the presence alone.

Thus, in the first embodiment, the exhaust gas temperature Tex which can be raised to the temperature T2 (for example, about 800 ° C.)
Can be further increased. That is, referring to FIG. 12, normal control, one-stage injection (in the case of the first embodiment),
Although the exhaust gas temperature Tex in each of the stage injections (in the case of the second embodiment) is shown in comparison, as is clear from the figure, at the time of the normal control, the exhaust gas temperature Tex is not more than the activation lower limit temperature T1 (for example, , 400 ° C.), whereas in the case of the first embodiment, the temperature T2 (for example, 8
In the case of the second embodiment, the temperature can be further increased to a higher temperature T3 (for example, about 900 ° C.). This makes it possible to heat the catalytic converter 9 more quickly and activate it earlier.

Referring to FIG. 13, normal control, 1
The emission amount of the unburned hydrocarbon THC in each of the two-stage injection (in the case of the first embodiment) and the two-stage injection (in the case of the second embodiment) is shown for reference, but as shown in FIG. In the first embodiment, the unburned hydrocarbon THC emission is reduced more than in the case of the first embodiment, and is further reduced when the two-stage injection is performed as in the second embodiment. . Thus, the emission of harmful substances into the atmosphere during the exhaust gas temperature raising control, that is, when the catalytic converter 9 is not activated, is suitably prevented. In particular, when the two-stage injection is performed as in the second embodiment,
The effect of preventing the emission of harmful substances is considered to be great.

As described above, in the exhaust gas temperature raising apparatus of the present invention, when the temperature Tcc of the catalytic converter 9 falls and the catalytic function decreases in the control device for the direct injection gasoline engine, the fuel is increased in the compression stroke. The fuel is injected and rich in the cavity 1c of the piston 1b (for example, 8 to 10).
And the incomplete combustion products (HC, CO, etc.) generated by the rich combustion are reduced in the expansion stroke by O2 in the air in the combustion chamber 1a other than in the cavity 1c.
_The exhaust gas temperature Tex is made to rise more slowly than during normal control by reacting slowly with ₂ .

Therefore, it is possible to appropriately prevent thermal energy from contributing to the expansion work, which is generated when the additional fuel is injected and burned at an early stage of the expansion stroke as in the prior art.
In addition, the catalytic converter 9 can be satisfactorily heated and reliably activated while preventing deterioration of fuel efficiency. In addition,
In the present embodiment, when the control is changed from the normal control to the exhaust gas temperature raising control, it is assumed that the ABV 50, that is, the air amount adjusting means is not changed and the intake air amount is maintained at a substantially constant state for switching. At the start of the exhaust gas temperature rise control
May be controlled so as to positively increase the intake air amount and also increase the fuel injection amount to further obtain the exhaust gas heating effect. At this time, it goes without saying that the engine control parameters such as the fuel injection timing and the ignition timing are controlled so that a torque step does not occur when shifting to the exhaust temperature raising control. In this embodiment, the ABV 50 is used as the air amount adjusting means. However, when an electronic throttle valve for electrically controlling the throttle valve is used, this electronic throttle valve is used as the air amount adjusting means, and the electronic throttle valve is used. May be changed at the time of exhaust gas temperature rise control.

Further, in the above embodiment, the direct injection gasoline engine using the tumble flow has been described. However, the present invention can be applied to a direct injection gasoline engine using the swirl flow. That is, the engine may be any engine as long as it is capable of injecting fuel from the fuel injection valve at least during the compression stroke and then igniting sparks to perform stratified combustion.

[0067]

As described above in detail, according to the exhaust gas temperature raising apparatus of the first aspect, the exhaust gas temperature can be raised without using combustion (reburning) for raising the exhaust gas temperature in expansion work. The catalyst can be quickly heated and activated early without deterioration of fuel efficiency.

Further , according to the exhaust gas heating apparatus of the second aspect,
By delaying the fuel injection timing during the compression stroke,
It is possible to raise the exhaust temperature even better,
The catalyst is quickly heated without deteriorating fuel economy and activated early.
Can be made. According to the third aspect of the present invention, the combustion can be slowed down, and the exhaust gas temperature can be more effectively increased in addition to the delay of the fuel injection timing . Also,
According to the exhaust temperature increasing device according to claim 4, after the main combustion, when the incomplete combustion product in expansion stroke is diffused around the combustion chamber with the descent of the piston, leading to fuel injected by the generation Preflame reaction This pre-flame reaction product functions as an ignition inducer, allowing incompletely combusted products to react very well with O ₂ and re-combust. It can be activated earlier.

According to the fifth aspect of the present invention, there is provided the exhaust gas heating apparatus according to the first aspect.
An amount that does not contribute to the expansion work by the amount of fuel by the preceding injection, and that the preflame reaction product suitably serves as an ignition inducer and can raise the temperature of the exhaust gas ( internal combustion engine
With related total amount of from 10% to 40% of the injected should do fuel per one stroke cylinder 1 cycle), can be further activated early more effectively implement catalyze the exhaust gas Atsushi Nobori .

Further, according to the exhaust gas temperature raising device of claim 6 ,
When the exhaust gas temperature rises, the fuel injection amount in the compression stroke can be increased in accordance with the air amount increase by the air amount adjusting means, and the exhaust gas temperature can be more suitably increased. Further, in the exhaust gas heating apparatus according to claim 7,
According to this, combustion can be slowed down and exhaust gas
Can be applied.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an engine control device including an exhaust gas heating device of the present invention.

FIG. 2 is a diagram showing a fuel injection control map during normal operation.

FIG. 3 is a flowchart illustrating a main routine of a temperature raising control of the exhaust gas temperature raising device according to the first embodiment.

FIG. 4 is a flowchart illustrating an exhaust gas temperature rise control routine according to the first embodiment.

FIG. 5 is a diagram showing, in chronological order, a state inside the combustion chamber when the exhaust gas temperature raising control of the first embodiment is performed, and is a diagram for explaining the operation of the exhaust gas temperature raising control of the first embodiment.

FIG. 6 is a graph showing the results of Example 1 and showing the relationship between the change in crank angle from near TDC and the heat release rate during the expansion stroke.

FIG. 7 is a flowchart illustrating an exhaust gas temperature increase control routine according to a second embodiment.

FIG. 8 is a graph showing a relationship between a fuel ratio with respect to a total fuel injection amount and an exhaust gas temperature Tex during an intake stroke preceding injection in the second embodiment.

FIG. 9 is a graph showing a relationship between a fuel ratio and a discharge amount of unburned hydrocarbon THC from an exhaust port in an intake stroke preceding injection in Embodiment 2.

FIG. 10 is a diagram showing, in chronological order, a state in a combustion chamber when an intake stroke preceding injection according to a second embodiment is performed.

FIG. 11 is a graph showing the results of Example 2 and showing the relationship between the change in crank angle from near TDC and the heat release rate during the expansion stroke.

FIG. 12 is a diagram showing a comparison between exhaust temperatures Tex in normal control, one-stage injection in the first embodiment, and two-stage injection in the second embodiment.

FIG. 13 is a diagram showing the emission amount of unburned hydrocarbon THC in each of normal control, one-stage injection of the first embodiment, and two-stage injection of the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 In-cylinder injection spark ignition type internal combustion engine 1a Combustion chamber 1b Piston 1c Cavity 8 Fuel injection valve 9 Catalytic converter 9a Lean NOx catalyst 9b Three-way catalyst 21 Crank angle sensor 23 Electronic control unit (ECU) 26 Catalyst temperature sensor 35 Spark plug 50 Air bypass valve (ABV)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02B 17/00 ZAB F02B 17/00 ZABF 23/10 ZAB 23/10 ZABZ F02D 41/34 ZAB F02D 41/34 ZABF 43/00 301 43/00 301B 301J ZAB ZAB F02P 5/15 F02P 5/15 ZABB (72) Inventor Hiromitsu Ando 5-33-8 Shiba 5-chome, Minato-ku, Tokyo Mitsubishi Motors Corporation (56) References JP-A-4 JP-A-231645 (JP, A) JP-A-6-93902 (JP, A) JP-A-8-232645 (JP, A) JP-A-8-200137 (JP, A) JP-A-10-103117 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) F02D 41/02 325 F01N 3/24 F02D 43/00 301 F02D 41/34 ZAB F02P 5/15

Claims (7)

(57) [Claims] An exhaust temperature rise of an in-cylinder injection type internal combustion engine having a fuel injection valve for directly injecting fuel into a combustion chamber and injecting fuel from the fuel injection valve at least during a compression stroke to perform spark ignition and stratified combustion. A fuel injection control means for controlling the fuel injection valve so as to inject in the compression stroke an amount of fuel that locally generates an over-rich mixture around the ignition plug during operation of the engine that requires an exhaust temperature increase. And when the fuel injection control means is controlling the fuel injection valve, the fuel injected and spark ignited in the compression stroke causes incomplete combustion in an over-rich state around the spark plug. And an engine control means for controlling an engine control parameter so as to mix and burn with excess oxygen in the cylinder in accordance with the internal flow. 2. The fuel injection control device according to claim 2, wherein
That the control means controls the fuel injection valve.
The engine control parameters in the compression stroke.
All fuel injection timings should be controlled by engines that do not require
Delay the fuel injection timing of the compression stroke during gin operation
The exhaust gas heating device according to claim 1, wherein: 3. The fuel injection control device according to claim 2, wherein
When the engine is running when exhaust temperature rise is not required
When the fuel injection timing of the compression stroke is delayed,
The ignition timing as an engine control parameter
Delayed ignition timing when engine is not required
3. The exhaust gas heating device according to claim 2, wherein
Place. Wherein said fuel injection control means, a portion of the fuel from the initial <br/> intake stroke until the initial of the compression stroke, before
Locally producing the over-rich mixture in the compression stroke
And controlling the fuel injection valve to inject prior to order of fuel injection, exhaust gas temperature increasing device according to claim 1 to 3, wherein. The amount of wherein said preceding to injection should do fuel, before
Injection should do fuel to gulp cylinder per cycle of the serial internal combustion engine
Characterized in that it is set to 10% to 40% of the total amount of the exhaust temperature increasing device according to claim 4, wherein. 6., further comprising an air quantity adjusting means for adjusting the amount of air introduced into the combustion chamber, the air quantity adjusting means, when the engine operating at least the exhaust Atsushi Nobori is required to increase the amount of air Wherein the fuel injection control means is controlled by the air amount adjusting means.
Before such fuel injection quantity increasing size in accordance with the increasing size of the incoming air volume
And controlling the serial fuel injection valve, according to claim 1 Symbol <br/> mounting of the exhaust temperature increasing device. Wherein said engine control means, the control of the fuel injection valve by the fuel injection <br/> control means is being performed
Can, the ignition timing of the engine control parameter, the exhaust is characterized by delaying than the ignition timing at the time of heating is required Tei no engine operating exhaust Atsushi Nobori apparatus according to claim 1.